The University of Florida Astrophysics Seminar is held on Wednesdays at 3:00pm. During the Fall 2022 semester, seminars will be held in-person in NPB 2165. Seminars may also be broadcast over Zoom, details TBD.

Fall 2022 Schedule

September 21: Jeff Andrews (University of Florida)

Title: It Takes Two to Tango: Modeling Binary Stellar Populations in the Gravitational Wave Era

Abstract:

Between the discovery of gravitational waves from dozens of merging compact objects and the advent of micro-arcsecond astrometry realized by the Gaia space telescope, the study of the complexities binary stellar evolution - including mass transfer, tides, and r-process nucleosynthesis - has taken on a new urgency. In this talk, I will describe the current status of modeling binary star populations as well as several critical shortcomings that my collaborators and I are working to systematically address. In particular, I will focus on how we are using modern statistical and machine learning methods using dedicated supercomputers to improve our physical models of binary star populations.

September 28: Felipe Guzman (Texas A&M University)

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October 5: TBD

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October 19: Tiziana Di Matteo (Carnegie Mellon University)

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October 26: TBD

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November 2: Lee McCuller (Caltech)

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November 9: Amy Reines (Montana State University)

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November 16: TBD

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November 23: TBD

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November 30: TBD

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December 7: TBD

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Spring 2022 Schedule

January 12: Special Colloquium: Craig Group (University of Virginia)

Title: Expanding the search for dark matter with new accelerator-based experiments

Abstract:

The evidence for dark matter is strong. However, the constituents of dark matter are still unknown, and the viable possibilities span a very large mass range. Specific scenarios for the origin of dark matter sharpen the focus on a narrower range of masses: the natural scenario where dark matter originates from thermal contact with familiar matter in the early Universe requires the DM mass to lie within about an MeV to 100 TeV. Considerable experimental attention has been given to exploring Weakly Interacting Massive Particles in the upper end of this range (few GeV - ~TeV), while the region ~MeV to ~GeV is largely unexplored. Most of the stable constituents of known matter have masses in this lower range, tantalizing hints for physics beyond the Standard Model have been found here, and a thermal origin for dark matter works in a simple and predictive manner in this mass range as well. It is therefore a priority to explore. If there is an interaction between light DM and ordinary matter, as there must be in the case of a thermal origin, then there necessarily is a production mechanism in accelerator-based experiments. The most sensitive way, (if the interaction is not electron-phobic) to search for this production is to use a primary electron beam to produce DM in fixed-target collisions. The Light Dark Matter eXperiment (LDMX) is a planned electron-beam fixed-target missing-momentum experiment that has unique sensitivity to light DM in the sub-GeV range. I will give an overview of the theoretical motivation, the main experimental challenges and how they are addressed, as well as projected sensitivities in comparison to other experiments.

February 2: Alexx Perloff (Univ. of Colorado)

Title: Searching for a Strongly Coupled Dark Sector with the CMS Detector

Abstract:

Searches for long-lived particles (LLPs), especially those associated with a dark matter (DM) candidate, have become a major focus of the Compact Muon Solenoid (CMS) physics program. During Run 2 of the Large Hadron Collider (LHC) at CERN, CMS became the first experiment to publish a search for a strongly coupled dark sector which contains a composite dark matter particle. This model contains a striking phenomenological signature consisting of emerging jets, whose tracks seem to appear not from the proton-proton collision vertex, but from multiple vertices within the CMS tracking detector. I will discuss this search as well the updated and ongoing version of the search. I will also discuss ongoing work to upgrade the CMS level-1 hardware trigger in order to prepare this system for the High Luminosity LHC (HL-LHC) with its unprecedented numbers of simultaneous proton-proton collisions. I will focus on the parts of the system which reconstruct the trajectories of charged particles, how these tracks are used by the downstream trigger systems, and how these upgrades will enable future dark sector searches at CMS.

February 9: Dylan Rankin (MIT)

Title: Novel Methods for Enabling Discovery at the LHC and Beyond

Abstract:

The discovery of the Higgs boson in 2012 was a momentous achievement for the LHC experiments and high energy physics in general. However, the LHC has not yet produced a discovery of physics beyond the Standard Model, and therefore both measurement and searches must begin to adapt and explore regions of phase space that have been left uncovered up until now. Doing so most effectively will require novel methods of data acquisition and analysis. In this talk I will present work from the ongoing development of the Compact Muon Solenoid (CMS) Level-1 trigger system upgrade for the High-Luminosity Large Hadron Collider. I will also discuss a new search at CMS for a light resonance decaying to two leptons which makes use of novel machine learning training methods and architectures.

February 16: Tamara Vazquez Schroeder (CERN)

Title: F(ℓ)avoured searches: leptoquarks - present status and future prospects

Abstract:

Recent anomalies observed in the B-meson sector may be one of our first promising hints of new physics beyond the Standard Model (BSM), suggesting that BSM may indeed have a different flavour structure than the SM. Leptoquarks, already hypothesised in the 1970s and predicted by many grand unified theories, are one of the preferred explanations of these tensions. It is also possible that they could be in reach at the collision energies at the Large Hadron Collider (LHC) at CERN. These hypothetical particles can mediate flavour-changing-neutral-currents and enable violation of lepton flavour universality. In the spirit of leaving no stones unturned, the ATLAS and CMS experiments at the LHC have developed a broad and diverse leptoquark search programme, paving the way to a potential discovery that could address many of the unanswered questions in Particle Physics.

February 23 (*special time: 3pm*): Bernard Kelly (NASA GSFC)

Title: Finding a Dance Partner for LISA: EM Emission from Black Hole Mergers in Plasma

Abstract:

Binary black hole (BBH) mergers provide a prime source for current and future interferometric GW observatories, especially by the Laser Interferometer Space Antenna (LISA), expected to launch in the mid-2030s. Massive BBH mergers may often take place in plasma-rich environments, leading to the possibility of a concurrent EM signal observable by traditional astronomical facilities. However, many questions about the generation of such counterparts remain unanswered, with details dependent on the precise form of the surrounding matter and magnetic field. I will discuss our current state of knowledge of these signals, and a set of investigations in numerical relativity with ideal general relativistic magnetohydrodynamics (GRMHD) to extract robust predictions that can inform multimessenger planning for the coming decades.

March 2: Michael Himes (UCF)

Title: Accelerating Computational Modeling via Neural Networks: Application to Exoplanet Atmospheric Retrieval

Abstract:

In physics and astronomy, computationally expensive forward models are often an integral part of preparing experiments/observations, analyzing data, and/or planning future instrumentation/telescopes. In many of these cases, machine learning (ML) models, such as neural networks (NNs), can offer a significant reduction in compute time with minimal loss in accuracy. We demonstrate this approach on the problem of exoplanet atmospheric retrieval, which involves on the order of 10^5 -- 10^6 radiative transfer (RT) model evaluations. We find that the ML RT approach yields the same scientific conclusions as the traditional method, while requiring ~1000x less compute cost. We present our open-source software packages that implement this technique, and we discuss broader applications of this NN surrogate modeling approach.

April 6: Kate Dooley (Cardiff University)

Title: Searching for signatures of quantized space-time and other physics mysteries with precision laser interferometry

Abstract:

The detection of gravitational waves required the design and construction of large laser interferometers that push the limits of precision measurement techniques. The extreme sensitivity of these instruments begs the question whether they -- or similar ones -- can be used to shed light on other questions in fundamental physics. One of the first experiments to probe this alternate use of gravitational wave detector technology was the Fermilab "holometer", a set of co-located 40m-long laser interferometers designed to search for the potential quantization of space-time.

I will present a bit of this history and then introduce our experiment at Cardiff: table-top co-located interferometers that will be more displacement-sensitive than the original holometer thanks to an increase in laser power and the application of squeezed vacuum states of light. Recently widened theoretical interest has renewed the motivation for the search for signatures of quantized spacetime and new predictions are currently being consolidated. The Cardiff interferometers will also be able to set new upper limits on scalar field dark matter, and they will be the most sensitive high-frequency and broadband (10 MHz to 100 MHz) gravitational-wave detectors to date.

Fall 2021 Schedule

September 22: Angelo Ricarte (Center for Astrophysics/Harvard)

Title: Supermassive Black Holes from Microparsecs to Megaparsecs

Abstract:

We believe that a supermassive black hole lurks at the center of every massive galaxy, where they can shine as an active galactic nucleus (AGN) when supplied with gas to accrete.  These black holes are believed to be important for regulating gas cooling in massive galaxies and clusters via "AGN feedback," whose details are poorly understood.  The problems of supermassive black hole growth and feedback span roughly 10 orders of magnitude in spatial and temporal scale, an intractable problem for a single simulation.  In this seminar, I will discuss my theoretical work spanning this range in spatial scales: from modeling AGN central engines for the Event Horizon Telescope, to studies of the black hole-galaxy co-evolution with the Romulus cosmological simulations and semi-analytic models.  These studies help stitch together properties of AGN central engines and how they are connected to their host galaxies.
Link to recording

October 6: Astrid Lamberts (Observatoire de la Côte d'Azur)

Title: Neutron stars and black holes, what do we know of the astrophysical populations observed with GW?

Abstract:

The last 5 years have brought the first detections of binary black hole mergers, binary neutron star mergers, and the merger of mixed neutron star-black hole pairs was announced very recently by the LIGO/Virgo/KAGRA collaboration. To date, more than fifty detections have been made public, allowing for the first statistical studies of the underlying populations. After a brief introduction to GW detections, I will present general trends that can be inferred from the observed population, focussing mostly on the binary black holes. Then I will highlight a few recent « exceptional » detections, including the neutron star black hole merger events. I will explain how these discoveries are connected to massive stellar evolution, high energy astrophysics and global star formation accros cosmic time.

November 3: Benny Trakhtenbrot (Tel Aviv University)

Title: New Types of Transient Phenomena from Accreting Supermassive Black Holes

Abstract:

Our understanding of the evolving population of supermassive black holes (SMBHs) beyond the local universe is fundamentally limited to actively growing SMBHs, where relatively stable accretion of gas persists over several hundreds of millions of years. A growing number of transient phenomena in galaxy nuclei have recently begun to shed new light on SMBH demographics and the physics of gas accretion onto these objects, tracing events where this accretion has drastically intensified, diminished, and/or otherwise disturbed. These include “changing look AGN”, and other, yet poorly understood UV-bright flares from accreting SMBHs. I will review some of these new classes of transients, focusing on new results obtained with responsive, multi-wavelength follow-up observations. While these events observationally differ from the (stellar) tidal disruption events known to date, the physics behind them may be interlinked. Together, these phenomena can greatly advance our understanding of SMBH accretion, teach us how and why SMBHs turn their accretion “on” and “off”, and reveal the sought-after signs of super-Eddington accretion. I will finally mention how new surveys, such as the SDSS-V, are going to discover & survey many more SMBH-related transients.

November 17: Orion Sauter (Univ. of Florida)

Title: Simulating LISA for Mission Planning

Abstract:

The Laser Interferometer Space Antenna (LISA) is set to launch in the 2030s, and measure gravitational waves in the mHz band. The detector consists of three spacecraft orbiting the Sun in an equilateral triangle, each carrying two free-falling test masses. This system must be kept in stable orbit, and avoid disturbance of the test masses for the duration of the mission. To test different drag-free and attitude control systems (DFACS) prior to launch, the LISA Consortium has developed a number of simulations of the detector. We will discuss the methods behind these simulators, as well as their strengths and limitations.

December 1: Christopher Berry (University of Glasgow)

Title: New coalescing binary observations with LIGO and Virgo

Abstract:

Gravitational waves provide an unparalleled means of observing merging black hole and neutron star binaries. Following completion of the most recent LIGO and Virgo observing run (O3b), the LIGO and Virgo catalog of gravitational waves contains 90 candidates with a probability of astrophysical origin greater than 50%. Using these observations, it is possible to start to unravel the mysteries of how black holes and neutron stars form, and merging binaries evolve. We will discuss the results of O3b, reviewing how gravitational-wave data is analysed to understand the source population, and highlighting some of the most interesting discoveries to come from O3b.

December 8: Evan Hall (MIT)

Title: The future of ground-based gravitational-wave astronomy

Abstract:

Ground-based gravitational-wave astronomy is poised to enter a new era in the next decade. A global network of new observatories will detect collisions of black holes and neutron stars across the entire stellar history of the universe, and will probe dense matter, extreme gravity and fundamental physics with greatly improved sensitivity compared to today’s observatories. In the United States, planning is underway for Cosmic Explorer, a 40 km observatory that will leverage advancements in a number of technologies — nonclassical states of light, high-quality materials, inertial isolation, geophysical engineering, among others — to open a new window onto the gravitational-wave universe.

Other Events

Students may receive credit for attending the Astrophysics Seminar by registering for PHY 6391.